First man-made satellites

For hundreds of years people have been dreaming о flights. Yet the dream remained only a dream till 1957 when people sent up the first man-made satellites. The man-made satellites are flying laboratories, equipped with the latest instruments and apparatus. The purpose of these laboratories is to investigate various types of radiations as well as the effects of the state of weightlessness on the human organism in the upper layers of the atmosphere.

The satellites revolve round the Earth just like planets. Their motion is governed by the same laws that govern the Moon's revolution round the Earth and the motion of the Earth round the Sun. Had there been no Earth's gravitation, they would have moved through airless space in a straight line at a uniform speed. It is the gravitation that makes them move round the Earth.

The force of gravitation which affects the satellite has a definite value. To counter-balance this force the satellite must keep to its orbit if it moves at a given speed. This speed must be approximately eight kilometers per second if the satellite moves at a relatively small distance from the Earth's surface.

The force of the Earth's gravitation decreases with the increase in the distance from the Earth. Therefore, a satellite moving along a higher orbit should have a lesser speed. If a satellite moved in different orbits — all within a thousand kilometers from the Earth's surface — the variations in the speed would be relatively small.

In order to be set on its orbit, the satellite has to be sent up at a great height and with the necessary speed. The satellite does not need any additional energy in order to move in its orbit. All it needs is the initial speed given it by the carrier rocket.

If the satellite's speed were much less than the necessary one, the satellite might drop and enter the denser layers of the atmosphere. It would lose its energy because of the friction of the air. If it dropped further and further, it would grow hotter and hotter and finally would burn up in the atmosphere.

The first satellite marked the beginning of the conquest of cosmic space. Now the day has come when manned space ships are leaving and will leave the Earth for distant planets, for distant worlds.

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